1. Field of the Invention
The field of the invention relates to data processing and in particular to processing secure and non-secure data using additional processing devices to perform tasks under control of a first data processor.
2. Description of the Prior Art
Data processing apparatus that can handle secure data are known and are generally arranged such that when the secure data is being handled the processor is operating in a secure mode. When operating in the secure mode the data processing apparatus can access secure data that is not accessible in a non-secure mode. To keep the secure data isolated from the non-secure processes switching between modes requires various handling routines to be run to ensure no leakage of secure data between the secure and non-secure sides. Thus, generally in response to a request for a secure service such as a cryptographic process to be performed the system makes an operating system call and enters privileged mode. From there a call is made to the secure mode and handling routines are performed to ensure that secure mode is entered correctly. The secure service can then be performed, after which the system switches back to non-secure mode, which requires further handling routines to be performed. Thus, if the secure service is only a small task the switching can be a very large overhead in performance.